Formaldehyde inflicts cytotoxicity by altering the glutathione redox balance

CARLA UMANSKY; MARCO SCHEIDEGGER; AGUSTÍN MORELLATO; MATTHIAS RIECKHER; MANUELA MARTINEFSKY; GABRIELA FERNANDÉZ; MARIELA BOLLINI; MARIA EUGENIA MONGE; BJORN SCHUMACHER; LUCAS PONTEL

Simposio; 22nd EMBL PhD Symposium ?The roaring 20s: A New Decade for Life Sciences?; 2020

EMBL

Cellular metabolism provides energy and molecules required for cell growth and development. However, some biological reactions such as histone and nucleic acid demethylations or the one carbon cycle can also generate formaldehyde (FA), which reaches blood concentrations of up to 45 µM. FA is a well-established genotoxic metabolite that might be abundant in highly proliferative cancer cells. To address how cancer cells cope with endogenous FA, we inactivated the FA-metabolizing enzyme alcohol dehydrogenase 5 (ADH5) in human colorectal carcinoma cells (HCT116). Despite active DNA repair, these cells presented a significant reduced tolerance to FA in viability assays showing signs of apoptosis. They also failed to form 3D-tumor spheroids in presence of blood concentrations of FA. Human preB leukemic cells (Nalm6) lacking ADH5 were also sensitive to blood levels of FA. An interrogation of DNA damage markers indicated FA triggered a P53 response in absence of ADH5. However, inactivation of P53 could not revert FA-induced cell death, suggesting that other cell-death signalling mechanisms take place. Further exploration revealed that FA induces the accumulation of reactive oxygen species (ROS) in cells lacking ADH5, suggesting an alternative cytotoxic mechanism of FA. By combining glutathione (GSH) potential sensors and ultraperformance liquid chromatography coupled with mass spectrometry we found that FA reacts with the redox active thiol group present in GSH forming S-hydroxymethyl-GSH and altering the balance between reduced and oxidized GSH. The toxicity of FA can be fully rescued by thiol-containing antioxidants, indicating that cell antioxidant defenses are a target of FA. This novel cytotoxic action of FA might have wide implications for Fanconi Anemia and Ruijs?Aalfs syndrome patients -all cancer-prone diseases whose onset have been linked to FA, as well as for cancer development in carriers of BRCA2 mutations.